1. Field of the Invention:
The invention relates to a method of spinning-in yarn on open-end spinning machines in which an interruption of the spinning process is followed by the stop of the sliver feed into the singling-out device whose combing roller keeps turning, and the rotor is stopped at least during its cleaning, and when the rotor has re-started the yarn end is returned to it and brought into contact with the fiber band being formed.
The invention also relates to a device for carrying out the method provided in the singling-out device of the spinning unit of an open-end spinning machine. The singling-out device comprises a body carrying therein a rotatably mounted combing roller around whose cylindrical surface, fitted with a clothing, there is provided a fiber transport channel, followed by a supply channel for feeding the fibers into the rotor, and in which there is related to the combing roller a sliver feed device for supplying a silver to the fiber transport channel.
The device for carrying out the method according to the invention can be applied on open-end spinning machines, both with an active rotor having ventilation apertures and producing underpressure by means of its own rotation, and with a passive rotor, without ventilation apertures, seated in an underpressure chamber connected to an underpressure source.
2. Description of the Related Art:
In open-end spinning machines, the spinning process must be resumed after each yarn interruption on each spinning unit. Yarn interruptions are caused, for example, by yarn rupture or the exchange of an empty bobbin for a full bobbin. Spinning is resumed by inserting the yarn end into the rotor of the spinning unit where the fibers deposited in the known way on the collecting surface of the rotor are connected to this yarn end and the draw-off motion of the yarn starts the process of continuous spinning. This whole process is called spinning-off.
Open-ended spinning machines can be divided into two types, depending on the way in which underpressure is produced: (1) those with active rotors fitted with ventilation apertures for producing underpressure in the rotor by means of its own rotation; and (2) those with passive rotors in which underpressure is generated by placing the rotor in an underpressure chamber connected to an underpressure source. Although the spinning-in operation in these two types show some differences, the feature common to both of them is that, after the interruption of the spinning on a spinning unit, the related combing roller keeps rotating, while the sliver feed is stopped. As a result, the rotating combing roller loosens fibers from the sliver end section, or also tears or breaks away parts thereof, and this process goes on for an indefinite time interval or until a servicing device comes. If the spinning-in is carried out on a fiber band made of a thus-damaged fiber end section, the quality of the spinning-in connecting section is poor, and the number of ineffective spinning-in attempts increases. A low quality spinning-in connecting section impairs the yarn suitability for its further processing in the textile industry, for instance in the knitting industry, because it leads to ruptures of the yarn while being processed, or to aesthetic defects of the final products.
The problem of producing a high quality spinning-in connecting section can be solved by tilting the sliver condenser of the feed device away from the combing rotor, but this solution is so complicated in design and production that it has not found acceptance.
CS 227 602 has disclosed a method of spinning-in yarn on an open-end spinning machine with a spinning rotor before which there is placed a singling-out device with a sliver feed device and with a combing roller. The spinning-in device returns the yarn into the spinning rotor for connecting it to the fiber band produced in the collecting groove of the rotor by re-starting the feed device that was put out of operation in the preceding phase, whereupon the yarn is again drawn-off from the spinning rotor. The spinning-in process is started after the rotor has been cleaned. The fibers contained in the fiber end section gripped in the feed device are led away from the transport path of fibers between the feed device and the spinning device so as to be completely removed from the spinning-in process.
The above method of spinning-in is, however, only a goal up to now not obtained by any device, because the leading of the fibers away from the fiber transport path is carried out after the spinning rotor has been cleaned, i.e., at a time when the spinning rotor already turns and, since it is an active rotor, its ventilation apertures produce underpressure while turning.
The fundamental condition for the device to function is the elimination of the underpressure in the rotor. This may be obtained in either of two ways, either by increasing the underpressure in the waste channel intended to lead the waste away from the transport path of the fibers, or by closing the fiber supply channel intended to feed the fibers from the combing roller into the rotor, for instance by applying the air stream to the supply channel in the direction opposite to the fiber flow, as described in CS AO 227 602. The production and technological application are so complicated that they have not permitted the use of this method in practice.
An improvement of this method was intended by the solution described in DE OS 34 36 295 in which the waste channel in the singling-out device reaches as far as the front side of the singling-out device. An aperture in the front side of the singling-out device can receive an ancillary suction tube having an aperture matching with the waste channel in the final position of said suction tube. The inner space of the suction tube is connected to an underpressure source feeding the fibers presented from the clothing of the combing roller. The chief drawbacks of this device are its ambiguity and the difficulty to obtain the exact mutual position of the components required in order to avoid irregularities in the introduction of the tube into the waste channel.
Another solution to the problem consists in sucking away the damaged fibers through the waste channel or through a special suction channel prior to the spinning-in proper. The feed device is started for a predetermined time interval so as to carry out a kind of pre-feed of the sliver. It is then stopped, the damaged fibers are sucked away, and only then does the spinning-in process properly begin.
Such a device has been further improved by EP 374 982 A1, in which the suction tube is laid to the front side around the suction channel mouth. Its drawback consists in the imperfect sealing of the connection on the front side of the spinning unit and in the necessity to suck away considerable amounts of air requiring a correspondingly mighty underpressure source.
Another improvement is described in EP 374 983 A1, in which a tube for supplying pressurized air into the suction channel is connected to the mouth of the suction channel. The pressurized air produces, at the place of the waste channel mouth, an injection action in consequence of which the fibers are sucked off from the clothing of the combing roller during the sliver pre-feed.
This solution also puts heavy requirements on the pressurized air source. Like all preceding solutions, this method cannot remove from the combing roller clothing all impurities and fiber rests.
For passive rotors, a method of spinning-in yarn on open-end spinning machines has been described in U.S. Pat. No. 4,059,946, in which the yarn end is put back to the spinning rotor running in an underpressure chamber, placed on the fiber band being produced in the rotor from the singled-out fibers being supplied, connected to the fiber band, and drawn-off. For producing a fiber band suitable for the spinning-in operation, the sliver feed is engaged for a determined time interval before said yarn end is placed on the fiber band, the yarn is again drawn away, the feed is then interrupted again, and finally again engaged only for the spinning-in operation properly.
During the first sliver feed, lasting for a predetermined time interval, the singled-out fibers, comprising the damaged fibers of the fiber end section, are led away due to the underpressure existing in the underpressure chamber through the resting rotor into the underpressure chamber and from it into the suction tube. The rotor must be stopped in this phase.
Problematical in this solution is the removal of all damaged fibers from the combing roller clothing and from the rotor.
For this reason, a device has been developed, described in WO 86/01235, in which an ancillary suction channel enters into the fiber transport channel provided around the combing roller clothing. The ancillary suction channel enters behind the fiber feed channel, supplying the fibers into the rotor, seen in the direction of rotation. The ancillary suction channel is connectable to the underpressure source during the sliver pre-feed, and when the underpressure is applied to the ancillary suction channel, the pressurized air supply into the underpressure chamber of the rotor is interrupted so that the fibers are being sucked into the ancillary suction channel.
In spite of its considerably complex design, the chief drawback of this solution consists of the fact that not all impurities sticking to the clothing of the combing roller can be perfectly removed.